A hard disk drive (HDD) positions a magnetic-recording head by servo control using servo patterns on a magnetic-recording disk and writes data to, or reads data from, the magnetic-recording disk at an address designated by a host. An operation for writing servo patterns to magnetic-recording disks is called servo writing; and, servo writing is generally performed in the manufacturing of the HDD. As one type of a servo write operation, self-servo writing (SSW) is known which reads out data written by the HDD, itself, for head positioning and timing control to write servo patterns to magnetic-recording disks.
Development and design engineers engaged in the design of HDD technology are ever vigilant for more efficient and reliable methods for writing servo patterns to magnetic-recording disks. In particular, SSW is one technique for writing servo patterns to magnetic-recording disks which is very efficient, because SSW does not require the utilization of a separate servo writing tool to write servo patterns. However, the reliance of SSW on previously written servo patterns for the writing of subsequent servo patterns creates the potential for registration errors in the servo writing process, which can substantially lengthen the servo writing process in attempts to recover from such registration errors. Therefore, HDD development and design engineers are interested in refining the SSW process to eliminate such sources of error.